A topographic map of the rock formations under the Norwegian Sea hangs on the wall of Sam Huisman's '98 office in Stavanger, Norway. Asked how he predicts where under the seafloor there's oil or gas, the geologist jokes, "Darts. Wherever the red dart lands."

The size of the Norwegian continental shelf that his employer, energy corporation ConocoPhillips, explores for oil and gas and the complex geologic conditions required to yield fossil fuel can make dart-throwing seem, some days, as good a method as any for finding it. Most days, though, Huisman takes a more scientific approach.

"The most informative broad-scale tool we use is seismic," he explained. Sound waves transmitted through the water into sub-sea rock layers send back echoes that describe those rocks. Huisman looks for places where rock faulting has formed "traps." Evidence of a trap, though, is no confirmation it's full of lighter-than-water oil or gas. To assess that, Huisman brings other data to bear: magnetic and gravitational fields, the temperature and chemistry of rock samples, and paleogeographic reconstructions of the region-how land masses have shifted over eons. Even when a particular trap looks like a good prospect on paper, there's no certainty the reservoir rock within will be permeable enough to allow its oil to be extracted.

Though the puzzle is complex, Huisman's bet is that there are additional oil fields with commercial viability somewhere under the Norwegian Sea. An earlier success story in the area is ConocoPhillips' Heidrun field, which yields 140,000 barrels of oil a day. The discovery of the next field-if there is one-will require gathering and analyzing much more data. Huisman explained that's because "complexity underground extends in three dimensions, and rock type can change over a couple thousand feet. Plus, the earth records a complex history; throughout geologic time, oil traps can be destroyed as easily as they form."

Though Huisman and his colleagues can be fairly sure about energy prospects in some areas of the Norwegian Sea, other areas will, he said, "be an enigma until tested by the drill bit. Once in a while we get lucky and strike oil. Quite often we're wrong. It's an ongoing process. We learn something new every day, and we're humbled by the magnificent diversity of the earth."

He may or may not be around when the time comes to put the X on the map and drill. This assignment, which began last June, is meant to train Huisman on a part of the world's geology very different from west Texas, his previous post. A year from now he could be exploring elsewhere.

Wherever on the planet he is, Huisman said he finds oil exploration "a pleasure and a challenge." At the same time, as a Christian who believes in stewardship, he feels its tensions. "Am I helping to poison the earth? Yes, we all are, every time we fill up our cars or heat our homes. Do we have a responsibility to look for other forms of energy? Yes, we must. But in the meantime, our own country needs energy. And growing economies around the world need fossil fuels to run tractors and build water treatment plants and do all the other things it takes to climb out of poverty."